Recently, in a variety of cases, including a case of coloring a paving face such as a sidewalk, an open space, a bridge and the like with various colors for presenting fine appearance, a case of coloring a pedestrian crossing and a tunnel for traffic safety, or a case of coloring a crotch of a street, a bus stop, and the like for improving the function of the street, so-called color paving has been carried out.
Generally, the color paving is carried out using a colored aggregate and using a pigment for a binder.
In the case of the former, there are natural ones such as silica sand and limestone, and artificial ones such as so-called light color aggregate available. They are all white and many of them are expensive.
On the other hand, with respect to the latter, there is a method for mixing a pigment to a heated asphalt mixture, however, the heated asphalt itself is originally dark brown and even if a pigment is added, it is difficult to provide the chromaticity or brightness of the pigment itself.
To solve the above-mentioned problems, there is a method for mixing a synthetic resin such as a petroleum type resin and an epoxy resin with a pigment. This method can make color paving with various light colors possible, however, it requires washing of facilities in the case of using existing asphalt facilities and inevitably involves complicated work and also it is required to transport the asphalt mixture in heated and melted state to a work site and therefore, it is needed to transport the mixture in a large quantity on a lorry to inevitably result in cost up in the case of a small scale paving. Moreover, in the case of mixing a pigment with a mixer, the pigment in fine powder state is scattered to the ambient environments to cause various problems, for example, adverse effects on workers or worsening of working environments.
To solve such problems, Japanese Patent Application Laid-Open (JP-A) No. 51-49532 reports cobble stone size or flaky molded bodies containing thermoplastic resins such as natural modified rosin resins and rosin polyesters, which are solid at a normal temperature, epoxy resins, and color pigments such as extender pigments. However, they are not used for paving after being mixed with aggregates, but at first the resin composition is heated, melted and used for paving, and then aggregates are spread and therefore, there occurs a problem in adhesion of the aggregates and the resin composition.
Japanese Patent No. 2,516,445 reports a granular or small lump type asphalt admixture containing commercialized asphalt as a thermoplastic resin and inorganic coloration pigment powders. However, the thermoplastic resin used here is a resin composition commercialized for so-called color paving and it is half-solid state itself at a normal temperature, the asphalt admixture is only a mixture obtained by mixing the commercialized asphalt and the pigments and crushing the mixture to certain sizes and therefore, there is a problem that the crushed particles of the admixture are stuck to one another at a normal temperature, especially in summer time.
Further, in the case the temperature is decreased at the time of a paving work, the fluidity of the asphalt composition is worsened to result in a possible problem in difficulty of a spreading and leveling work.
To prevent adhesion, Japanese Patent No. 2,562,094 reports a granular asphalt obtained by mixing a water suspension of sulfates, silicates, carbonates, hydroxides, and oxides of alkaline earth metals and zinc with commercialized asphalt and granulating and drying the mixture. The characteristic of this technique is that the above-mentioned fine powders are used as so-called suspension stabilizer so as to suspend asphalt, which is an oil component, in water and the use amount of the powders is consequently so high as to be 10 to 200 parts based on the amount of asphalt and since the fine powders contain a large quantity of water, there occurs a foaming problem at the time of producing an admixture by mixing the granular asphalt with aggregates and further it results in a problem that the work is dangerous and takes a long time.
Further, Japanese Patent Application Publication (JP-B) No. 58-10435 reports mixtures containing thermoplastic resins such as petroleum resins, petroleum type plasticizers with 200 or higher average molecular weight, and 0.1 to 5 parts by weight of vinyl acetate-ethylene copolymers. However, there is no description of the size and morphology of the obtained resin compositions and all of the compositions have a softening point of 45° C. or lower and are in semi-solid state at a normal temperature and at the time of using them, the compositions require to be heated and melted previously in a lorry vehicle or the like and their handling and workability is thus problematic.
Japanese Patent Application Laid-Open (JP-A) No. 62-189203 reports mixtures obtained by mixing 3 to 20 parts by weight of rubber type thermoplastic high molecular weight polymers (C component) and 0.3 to 15 parts by weight of urethane polymers (D component) of diene type liquid rubbers to mixtures of thermoplastic resins (A component) such as petroleum resins and petroleum type process oils (B component). However, the softening points of these resin compositions are all as low as 30 to 50° C. and as described above, the mixtures are in semi-solid state at a normal temperature to result in handling problems.
Further, Japanese Patent Application Laid-Open (JP-A) No. 4-359063 reports color paving binder compositions obtained by mixing 2 to 6 parts by weight of styrene-butadiene-styrene resins, 2 to 6 parts by weight of ethyl acrylate, ethylene ethyl acrylate, or ethylene vinyl acetate based on 100 parts by weight of base materials containing aromatic process oils and dicyclopentadiene type petroleum resins. However, there is no description of the morphology of the obtained binder compositions and further, oil type liquid substances exist in a ratio of 50% or more in the entire resin compositions and the obtained resin compositions are also in semi-solid state to result in a problem of handling difficulty. Further, basically, to produce admixtures, it is needed to feed the compositions to a mixer after the compositions are previously heated and melted by a lorry vehicle or the like and thus there is also a problem of workability.
Japanese Patent No. 2,688,447 reports color paving binder compositions which indispensably contain petroleum resins, aromatic heavy mineral oils, thermoplastic elastomers, and liquid maleated organic compounds having an average molecular weight of 300 to 10,000 and an acid value of 10 to 200. Although there is description that an ethylene-vinyl acetate copolymer and the like may be added as the thermoplastic elastomers, the use amount is a little and oil type liquid substances exist in a ratio of 50% or more in the entire resin compositions and the obtained resin compositions are also in semi-solid state having a softening point of 50° C. or below to result in a problem of handling difficulty, similarly as described above. Further, there is no description of the morphology of the color paving binder compositions at all.
The Japanese Patent Application Publication (JP-B) No. 49-15469 reports a method for mixing plasticizers and pigments, based on necessity, with heated mixtures of polyethylene waste products and 20 to 40% of petroleum resins on the basis of polyethylene. However, the method is insufficient in fusion and wettability to aggregates and also in strength of mixtures with aggregates to result in a problem of durability of a paved face.
In view of the above situation, it is an object of the present invention to provide a paving resin composition in small lumps which is melted within a short time, excellent in wettability and adhesion property to aggregates, and capable of providing a paved face excellent in durability and free from problems of deformation during summer and cracking during winter.
Another object of the present invention is to provide a paving resin composition in small lumps, containing a pigment and a specified thermoplastic resin composition, which does not cause any powder dust generation problem even in work sites, and is suitable for paving while being mixed with aggregates within a short time.
Further, other object of the present invention is to provide a paving asphalt composition which is free from discoloration with lapse of time and easy to be spread and leveled in paving work ground.